Posi-Melt^™ XLA Mixing Screws

Why Posi-Melt^™ XLA Mixing Screws?

The Posi-Melt^™ patented feed screw is a core change to the geometry of the antiquated general purpose “GP” screw technology developed in 1950s. The Posi-Melt's^™ unique flight design alters the flight pitch and root of the screw through the melting section making them un-tangential with each other disrupting laminar flow. The geometry increases plastic exposure to the barrel wall by up to 60% delivering a uniform homogenized melt. The Posi-Melt^™ is the most versatile screw technology available in the industry today for delivering a high-quality melt at a low manufacturing cost. The design has succeeded processing resins from LCP to PC and Rigid PVC with diameters from 14mm through 240mm.

The XLA mixer disrupts the melt stream, adds extensional strain, relaxation, and cross-flow for distributive mixing. The mixer land clearance is adjusted for added dispersion when required.

Since every plasticating screw design has melt quality homogeneity limitations when the requirement for output increases, we have designed a family of advanced screws that incorporate the core Posi-Melt™ technology to meet the most demanding applications. If a high level of melt homogeneity is achieved, the polymer will flow more consistently into the mold assuring more evenly filled cavities with less part weight variance void of common defects such as warping, short shots, color variance and weak weld lines.

To reach a high level of homogenization the polymer must be melted first, then distributed or dispersed. When the swept volume is greater than three diameters and/ or the residence time is under ninety seconds most OEM’s default to longer L/Ds because of the diminished melting capacity. We have proven that our technology can deliver a quality melt under these conditions by first exposing the polymer to the core Posi-Melt™ technology for melting purposes then adding our proprietary mixing technology for additional melting and distribution using conventional length 20:1 L/D designs.

To add a higher level of homogenization to the melt pool we developed a very effective distributive/dispersive mixer that works by forcing the polymer to change direction numerous times over a short axial distance and by adding extensional strain to the polymer by forcing the material to cross over a shallower land multiple times for added shear. A positive pumping angle and major flight OD wiping action assures a low pressure drop for high throughput yet pressurizes the channels for positive displacement for melt cleaning purposes. The design is very versatile, rows can be added, the number of slots determined and the clearance between the barrel ID and the Mixing Land can be changed to suit the polymer family. The mixer is used for virtually all resin groups when precise color matching is needed or the residence time and swept volume dictate.